1. Field of the Invention
The present invention relates to a signal processing circuit capable of holding data even when not powered and a method for driving the signal processing circuit.
2. Description of the Related Art
In recent years, circuit operation has become complicated with higher integration and an increase in size of a semiconductor integrated circuit. Further, with miniaturization of a process of a semiconductor integrated circuit, leakage current of a transistor is increased, which causes a problem in that excess power is consumed owing to the leakage current even when the semiconductor integrated circuit is not in operation.
In that situation, a power gating (power-off) technique by which power supply or stop of power supply is performed to respective related circuit blocks formed in a semiconductor integrated circuit so that power consumption due to leakage current in circuit blocks which are not used is suppressed has been proposed.
For example, Patent Document 1 discloses a semiconductor integrated circuit which includes: a switch formed using a MOS transistor between a logic circuit and a power source so that power supply and stop of power supply are collectively performed to circuit blocks; and an SRAM circuit which controls the substrate potential of the MOS transistor so that power consumption due to leakage current is suppressed. With such a power gating technique, power supply to circuits which are not used in the semiconductor integrated circuit can be stopped per circuit block, so that excess power consumption due to leakage current can be suppressed.
[Reference]
[Patent Document]
    [Patent Document 1] Japanese Published Patent Application No. 2003-132683